Hi again. I got a response from the author of SVE. He thinks that the VRO Viper overrides his Viper and there's not an issue with the Viper in his mod. This suggests that there's perhaps an issue in the VRO base mod or the VROified version of SVE. Beyond my ability to check and dig into this further, sorry.
Vipers don't appear to be built very often but the only two I've seen in my current game have been built with no Engines, shields or turrets, though they have had active missile launcher main weapons.
Is it possible to look at a saved game - where the ship ID is known - to figure out where the issue lies?